<!DOCTYPE html>
<html>
<head>
	<meta charset="UTF-8">
	<title>window对象</title>
</head>
<body>
	<script type="text/javascript">
		var a = 3;
		console.log(window.a);
		function hello(){
			alert(window.a);
		}
		window.hello();
	</script>
</body>
</html>